1. Field of the Invention
The present invention relates to an outlet expansion apparatus, and a delegate authentication method.
2. Description of the Related Art
In recent years, a technology called smart grid has been gaining attention. The smart grid is a technological framework to realize efficient power usage by constructing a new transmission network having a communication channel along with the transmission network and using this intelligent transmission network. The background idea of the smart grid is to realize efficient management of the amount of power use, swift handling of an incident when such an incident occurs, remote control of the amount of power use, distributed power generation using power generation facilities outside the control of a power company, or charging management of an electric vehicle. Particularly, effective utilization of in-house power generating stations using renewable energy by ordinary households or operators other than power companies and charging management of various electric vehicles typically including electric cars have been attracting considerable attention. Incidentally, renewable energy is energy generated without using fossil fuel.
Power generated by ordinary households or operators other than power companies is used by power generation operators. Remaining power after use by the power generation operators is currently purchased by power companies. However, purchasing power supplied from power generation facilities outside the control of a power company is a heavy burden to the power company. For example, amount of power supplied from photovoltaic power generation facilities depends on the weather. Moreover, amount of power supplied from in-house power generating stations of ordinary households depends on power use of ordinary households that largely changes day by day. Thus, it is difficult for power companies to receive stable power supply from power generation facilities outside the control of power companies. For the above reason, it may become difficult for power companies to purchase power in the future.
Thus, a home battery initiative that uses power generated by power generation facilities outside the control of power companies after temporarily storing the power in batteries has recently been gaining attention. For example, a method of using power generated by photovoltaic power generation facilities by storing such power in batteries and making up for shortages in the night or when the weather is bad is considered. Furthermore, a method of limiting amount of power received from a power company in accordance with the battery storage amount or using power stored in batteries in the daytime when power rates are higher by storing power, in batteries, supplied by a power company in the night when power rates are lower are considered. Also, batteries can store power as DC, which makes DC/AC conversion or AC/DC conversion during transmission unnecessary so that losses during conversion can be reduced.
Thus, various expectations regarding power management mingle with one another amid the smart grid initiative. To realize such power management, the smart grid initiative is premised on having a communication channel along with a transmission network. That is, exchanging information about power management by using this intelligent transmission network is assumed. However, in a region where a communication infrastructure is already built, instead of using a transmission network as a communication channel, information about power management may be exchanged by using a network constructed by the deployed communication infrastructure. That is, what is important in the smart grid initiative is how to efficiently manage power generation facilities and storage facilities that are not uniformly managed.
Each electronic appliance managed in the smart grid initiative is not enabled to receive power supply unless it is individually authenticated by a power management apparatus and unless the authentication is successful. Due to this mechanism, even if an unauthorized electronic appliance is connected, power is normally not illegally used by the unauthorized electronic appliance. However, if an electronic appliance that is modified without authorization so that it will pass authentication by the power management apparatus is used, power will be improperly used by that electronic appliance that has been modified without authorization. Furthermore, there is a risk that the security of the whole system managed by the power management apparatus is threatened by the electronic appliance that has been modified without authorization. For these reasons, a technology that enables to reliably identify each electronic appliance is desired.
For example, JP-A-2008-109849 discloses a technology of detecting, for a plurality of electronic appliances, a current waveform of current consumed by each electronic appliance as a feature, and transmitting the feature to a server. Furthermore, a technology is disclosed according to which the server that received the feature compares the received feature and a feature registered in advance in a database and identifies each electronic appliance. The feature described in the above patent document is a change in current consumption, an average value, a peak value, an effective value, a crest factor, a form factor, a settling time of current change, a conduction time, a peak position, a time difference between a peak position of a power supply voltage and a peak position of current consumption, or a power factor. When using the technology described in the above patent document, each electronic appliance can be identified more reliably than when relying on authentication.